issue2551042 - add extra \ to \w in raw string url_to_regex. Not sure

why this is needed. Maybe something changed in how raw strings are
interpreted? Without patch causes crash:

 re.error: bad escape \w at position 2

under python 3.7

Also tried to add python 3.7 (hopefully 3.7.3) to travis.

Author: rouilj

.travis.yml

@@ -4,6 +4,7 @@ python:
   - 3.4
   - 3.5
   - 3.6
+  - 3.7
 
 sudo: false
 

roundup/rest.py

@@ -244,7 +244,7 @@ def parse_accept_header(accept):
 class Routing(object):
     __route_map = {}
     __var_to_regex = re.compile(r"<:(\w+)>")
-    url_to_regex = r"([\w.\-~!$&'()*+,;=:\%%]+)"
+    url_to_regex = r"([\\w.\-~!$&'()*+,;=:\%%]+)"
 
     @classmethod
     def route(cls, rule, methods='GET'):